VOIP and Remote Operating Applications and Ham Radio

Most present day government communication centers that use analog systems
happen to have a VOIP based dispatch console. Many remote sites are tied
together using over fiber. This analog to VOIP patching
is something that we are presently also embracing in ham radio with IRLP,
EchoLink, Yeasu
WIRES II, and the like. (See VoIP
and Amateur Radio overview By Steve Ford, WB8IMY from QST Feb 2003)

A different hardware board for each of these proprietary VOIP systems that you
want to support is required. You also need a need a multi-port repeater
controller, to support each hardware boards analog breakout. This seems redundant to me, and is something
that slows the advancement. IRLP seems to be the system of choice because
it runs on the Linux operating system. This is because Linux is much more
stable that Windows, and is an open source development.

Imagine how smoothly and fast things would have unfolded if everything was
open source, and no one had to waste time reverse engineering other peoples
secrets.

The ARRL made a
Interoperability statement in October 2007. This is a pretty serious
issue as there a number of proprietary digital voice radio systems out
there. None of them natively talk to each other.... Interoperability is
one of Amateur Radio's distinguishing features; losing it would be a giant step
backward.

There are some keys to consider when it comes to interoperability. The
lowest common denominator (aside from frequency) would seem to be the modulation
type. D-Star is GMSK, APCO-25 and pretty much everything else is 4FSK
modulation. Upon that you have a MAC layer level access protocol, then the
actual codec converting the voice to digital. Electronics is so PIC/chip
based, modulation changes can be changed without necessarily changing
components.

As long as there is a hardware common ground modulation type or ability to
speak/receive multiple types (like they did with 802.11b & g - DSSS/OFDM),
firmware should be able to be written to take care of any MAC layer differences.
Transcoding can take care of the differences between the various codecs.
This is where a platform like Asterisk shines.

Remote Operating

In 2010, Mikael Styrefors, SM2O unveiled (Remote
Rig) perhaps
the most elegant ways to operate remotely. It involves no computer, just
two Remote Rig Control (1258MkII) units. The front panel resides
with the client while the rest of the rig remains at the host.
Both devices connect to Internet routers via Ethernet cables.

RRC boxes are built around reliable ARM microprocessor, and
are an intuitive way of utilizing existing VolP technology. Control
and remote RRC units utilize three communication channels; a simpletext-based
SIP protocol is utilized for radio-to-radio communication, while a UDPdatagram
protocol is used for control and audio streams. The RRC unit also providestwo additional serial ports for connecting devices such as an
amplifier anda rotator control.

Remote station operation in recent years has increased in popularity.
In enables Amateurs in apartments and other similar situations
flexibility.

Hamlib
- The Ham Radio Control Libraries, Hamlib for short, is an independent
development effort to provide a consistent interface for programmers wanting to
incorporate radio control in their programs. Hamlib is not a complete user
application, rather, it is a software layer intended to make controlling various
radios and other shack hardware much easier. Hamlib will allow authors of such
software as logging programs, digital communications programs, or those wanting
to develop the ultimate radio control software to concentrate on the user
interface and the basic function of the program rather than radio control.

While IRLP holds promise, a large part of the hold up on outside and
additional developments for IRLP
seems to be related to the fact that parts of the IRLP system (the binaries that
talk to his hardware board) are
not open source. This to me doesn't seem to be in the true spirit of
amateur radio. I also read rumors (July 06) that the IRLP system designer (David
Cameron, VE3LTD) had
developed a similar system to IRLP that is being used commercially, and this to
may be part of his proprietary design reasoning. Another reason the
board design is unpublished is that the board is the IRLP designers only source
of funding to keep things alive. Also to cut down on the number of
questions/problems from the non-technical savvy. While neither of these
are bad, it still doesn't let technical savvy people do much more than talk over
the network. I & others could be developing and contributing ideas
though experimentation.

IRLP started in 1997 with Windows and VocalTec's iPhone and a WB2REM
interface. David, VE3LTD realized in 6 months time that iPhone was not
very stable nor is it controllable. He also ran into a road black when
source code for iPhone was not available. David looked for an alternative,
and he started getting into using Linux as an operating system and Speak Freely
as a client/server. SpeakFreely was open source and he was able modify the
source code to his liking to create what we now have today for IRLP. He
then designed his own hardware board for PTT & COR logic.

EchoLink natively runs on the Windows operating
system and was developed by Johnathan, K1RFD, released in 2002..
He approached this whole concept initially with a view to improving a system
then running called "iLINK" (The iLINK system, first appeared around May 2001, was developed by Graeme Barnes, M0CSH, in Kent
England), which was an enhanced development from a voip system called IPhone, as
was IRLP. But read on.

Initially "Echolink" was un-named, but Johnathan K1RFD, and David, G3VFPstarted development to provide an alternative graphical user front
end to what was then the "iLINK" voip ham system, sometime in
late 2001, or early 2002. Unfortunately through no fault of Jonathans, as
he tried hard over quite a few months to communicate, with the owner of iLINK.
It proved a near impossibility, and reputedly it was stated by the author
of iLINK that no third party software would be allowed on iLINK. So
Jonathan decided to form another peer to peer voip system completely, using his
graphical interface. Which by the way was years ahead of the iLINK GUI.

Open source versions of the EchoLink software are available for Macintosh (EchoMac)
and Linux (echoLinux
aka CQiNet or SvxLink/Qtel),
but they may have limited features compared to the Windows version. At least
when comparing the desktop applications.

CQiNet
provides "theBridge", which is code that allows one to talk to
EchoLink network from Linux or a Mac platform by Skip WB6YMH started in
mid-2002. CQiNet is a family of
programs that combine Ham Radio with the Internet using Voice over IP (VoIP)
technology. Two programs are currently in the family, "theBridge"
and echoLinux. Thebridge
is a iLink/EchoLink compatable conference bridge that runs under various
versions of Unix as well as Windows EchoLinux is a EchoLink client program for
the Linux operating system. Compatibility with EchoLink and IRLP is
a goal.

TheLinkBox - is program Skip WB6YMH started in
2007. Its based off CQiNET and "theBridge" to support serial & parallel-port
interfaces as well as USB dongles. A full featured multiport hub or repeater
controller as well as a VoIP application.

Johnathan, K1RFD tolerates thebridge and EchoIRLP partly because he does not
sell EchoLink or any boards that are needed to make it work. Since Dave, VE3LTD
derives income from IRLP it should not be surprising that he's less tolerant.

While IRLP is not 100% open, some clever people working with David Cameron,
the IRLP system designer have managed to adapt theBridge so that one can have
the
inter-operability of EchoLink and IRLP using the IRLP hardware. This is
called EchoIRLP a project
by Tony, VK3JED.
Both networks are capable of GSM audio compression (standard for EchoLink and is
an option for IRLP as it normally uses ADPCM), and the transport protocols are
quite similar.

In
this case, those who worked with David, worked out the details where the IRLP binaries are talking to The Bridge which is in
turn talks to the Echolink network.

The iLink protocols (the basis of EchoIRLP) were reverse engineered by Tom,
WD4NMQ and Skip, WB6YMH without the author of iLINK Graeme, M0CSH (G7BHM)
blessing. Without reverse engineering there would be no EchoIRLP.

Taking this one step
forward, Svxlink is another step
in the right direction. The Svxlink project allows configuration a variety
of existing economical radio to PC interfaces, such as the VA3TO
interface. What's notable about Svxlink is they have a schematic also
released under the GPL so one can homebrew their own radio to PC interface.

IRLP-Repeater script - More info on using IRLP as a repeater. Includes configurable repeater hang time, courtesy tones, timeout
timer. SCCW for morse IDs, DTMF muting provisions, and anything else you can
script.

David Cameron, VE7LTD, is the guy that originated IRLP and "pieced
together" the code himself. Not being a professional programmer he said he
was aware that the code was not going to be the most elegant in the world.
When he put it up the GPL license his email was besieged daily by folks flaming
him about why he did something this way or that without providing any alternative. Finally in disgust he removed it from the GPL license and
continued doing it his "own" way. Thats why the IRLP looks
"quite horrible" as it does.

Misc:

N3GLV is trying to get some of the AMPR.ORG activity back up for ham-voip,
contact him (n3glv1963 [at] gmail.com if interested and/or e-mail WB6CYT brian
[at] ucsd.edu)

One Step Further - Asterisk Overview

Asterisk is an Open
Source PBX & Telephony Platform. It's often labeled as the future of
telephony.

PBX stands for private branch exchange. It is a machine that handles many
businesses telephones calls for you. Its main functions are to transfer calls to
different individual phones; play music when somebody is put on hold; to play
automated voice responses when a call is received; to provide an options menu
for the caller etc.

Asterisk allows one to build their own phone systems. It adds features,
functionality and reduces deployment costs in ways which; at first are a little
difficult to understand.

Most people don't know that Asterisk was designed from the beginning with
radio applications in mind.

Jim Dixon (WB6NIL) developed pioneering hardware and software and collaborated
with Mark Spencer of Digium to make Asterisk a reality. Jim says that
compatibility with Amateur Radio applications was always a design requirement
for his Asterisk work.

Steve Rodgers (WA6ZFT) is a longtime friend of Jim's and they co-developed the app_rpt
module and the Quad Radio PCI card
to interface radio equipment to Asterisk. Steve's company QRVC Communications originally
offered the Quad Radio PCI cards for
sale. They have much been replaced by USB devices.

Steve Henke (W9SH) wanted to use hardware that would provide baseband (receiver
discriminator and transmitter modulation) signal processing. This allows noise
squelch detect, RSSI, CTCSS and other signaling protocols to be done in software
and provide additional features. The answer to this need was found in a low
cost USB Sound Adapter. Steve and Jim collaborated on the chan_usbradio
driver and Steve's company Xelatec contributed the xpmr radio signal processing
routines under the GPL to the project.

In my case, ham radio first introduced me to VOIP, with Echolink
and IRLP in the late 90's. Since that time,
I've been playing with Asterisk.
Asterisk is some very powerful stuff, perfect anyone who is familiar with Linux
and likes to tinker.

Developments for an application layer to allow an existing IRLP systems to
have added functionality to speak (SIP/IAX2) to an Asterisk system could be a
very beneficial contribution to ham radio.

Asterisk with app_rpt
can be connected to almost any radio transceiver andnetwork
if you have the skills and patience to make the necessary interface andconfigurations.

Several different radio makes and models
are well supported by vendors whoprovide ready
made interfaces and cables.For frequency agile remote applications,
app_rpt can control a multi-band,frequency
programmable radio transceiver such as the Icom IC-706.

Radio Transceiver To Asterisk
Interfaces

We will now describe two well supported
hardware solutions for interfacing PTTradios to
Asterisk.

Universal
Radio Interface (URI) - The third and most recently developed radio interfaceis the USB Radio Adapter. The principle advantage of this
device is that ithas a low cost. For example you
can build your own radio cable by attaching itto a
$7.00 off-the-shelf commercial USB Sound Adapter. With the USB RadioAdapter,
CTCSS and other signaling encoding and decoding is done in thesoftware.
And, signal level setting is done in software so there are nophysical
adjustments to make that require access to the computer and taking thecovers
off to reach the potentiometers. Additionally, the URI can determine thereceived
signal level in software and use it for squelch and other features.

This USB solution is to facilitate Asterisk applications using
app_rpt,
AllStar Link and the "chan_usbradio"
channel driver. AllStarLink released
a USB controller in Feb 2008 thru DMK
Engineering This is proposed as a Universal Radio Interface, based in
the CM108 chipset.

A nice Linux platform with a nice audio platform like Asterisk
and the USB dongle for the hardware interfacing.... those are all a great start
towards a whole software based repeater controller. And if it had a
modular GUI front end like FreePBX, if think this would really be something.
A nice web-based GUI front end setup for CW ID's, voice messages using text
to speech, a scheduler etc. (See the IRLP
Visual Admin Console and Micro Node,
these are GUI projects)

Many hams have, and already support the IRLP hardware, and that
also runs on Linux. Wouldn't it be nice if there was an application that would
provide the inter-operability in much the same manor we have added support for Echolink?
(As I've mentioned, the idea of having to have different hardware board for each
VOIP system you want to support seems redundant.)

A different hardware board for each of these proprietary VOIP systems that
you want to support is required. You also need a need a multi-port
repeater controller, to support each hardware boards analog breakout.

The reason is all these systems take an analog audio mixing approach.
And this feeds the need for a multi-port repeater controller, to support each
hardware boards analog breakout.

Asterisk is the best foundation for digital mixing. Their
MeetMe conferencing application is a good example. It uses a hardware
timing base/source. When it comes to mixing digital audio streams its
often necessary to have a this to ensure that all packets are "in
phase" or "sync" with the remote end. Without this digital
distortion can be very noticeable, jittery, choppy sound.

IRLP lacks this digital mixing foundation and this is why you can only
make/take one connection at a time. You connect to a reflector to be in
conference. With EchoLink you can conference independently, but as noted
above it usually sounds choppy.

If you want to drive the IRLP board with any other software, its circuitry is
fairly simple, because it just talks to the parallel port. Someone would
need to code a driver to spy on the parallel port and sound card inputs and
outputs so that IRLP or Echolink can be run without modification.

From what I understand the logic signals PTT/COR toggle the "call on
hold" field and that's how the standard signaling is sent over a standard
SIP/IAX stream.

Cheap Asterisk radio
interface - consists
of a modified USB sound device. A channel driver exists in Asterisk that enables certain Cmedia CM108 based USB sound devices to provide
the hardware interface between both commercial and amateur private land mobile radio equipment.
A pre-fab version is available from DMK
Engineering.

Alert Interface -
This device connects a receiver, such as an "All Hazards" warning receiver, to an Asterisk PBX. The intended purpose is to allow the warning messages to be broadcast over the Asterisk paging system.